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Teleconverter with microscope direct projection

 
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kit1980



Joined: 18 Aug 2016
Posts: 123
Location: Bellevue, WA, USA

PostPosted: Thu Feb 01, 2018 7:12 pm    Post subject: Teleconverter with microscope direct projection Reply with quote

I use Olympus OM-D E-M10 Mark II camera on a microscope in "direct projection" via extension tubes. It set up parfocally with the microscope's eyepieces.

The problem is that the image is a bit too small for the sensor: the camera field of view is significantly larger than with the eyepieces, and the image quality (sharpness and aberrations) degrades very significantly outside of the central part.

I'm thinking of buying an Olympus teleconverter to attach in front of the camera, so I get larger image and smaller field of view. Do you think it will work? Will the parfocality with the eyepieces be preserved?
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Omax microscope with Nikon CF objectives
Olympus OM-D E-M10 Mark II camera
http://sdymphoto.com/
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19184
Location: Richland, Washington State, USA

PostPosted: Thu Feb 01, 2018 8:12 pm    Post subject: Reply with quote

Yes, this should work fine. From the standpoint of whatever optics you put in front of it, a teleconverter mounted on camera essentially just makes the sensor look smaller so it covers a smaller part of the optical image. Focus is not affected.

--Rik
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Pau
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Joined: 20 Jan 2010
Posts: 4441
Location: Valencia, Spain

PostPosted: Fri Feb 02, 2018 1:38 am    Post subject: Reply with quote

Take a look:
http://www.photomacrography.net/forum/viewtopic.php?p=146353#146353

I think that Waldo pwnell still uses this approach to take his wonderful photomicrographs, not sure.

http://www.photomacrography.net/forum/viewtopic.php?t=24814&start=0&postdays=0&postorder=asc&highlight=microscope+teleconverter
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enricosavazzi



Joined: 21 Nov 2009
Posts: 1046
Location: Stockholm, Sweden

PostPosted: Fri Feb 02, 2018 4:38 am    Post subject: Reply with quote

As far as I know, there is only one teleconverter for Olympus Micro 4/3 (the 1.4x Olympus MC-14, see http://savazzi.net/photography/olymc-14.html ). It is good but expensive, and optimized for long focal lengths (primarily the 300 mm prime and the 70-150 mm zoom). It cannot be attached to most other Micro 4/3 lenses, but an empty Micro 4/3 adapter without optics should not be a problem. I have used this teleconverter on Metabones Micro 4/3 adapters without problems. The bayonet itself is a standard Micro 4/3, no "funny business" extra lugs like in Nikon teleconverters.

It might be worth investigating whether a second-hand Olympus EC-14 teleconverter for 4/3 (not Micro 4/3) plus a 4/3 to Micro 4/3 adapter can be significantly cheaper. See for example http://savazzi.net/photography/olympus50-200.html . In this case, you need a 4/3 (not Micro 4/3) adapter on the microscope photo tube.

It may also be worth considering a teleconverter for APS-C Nikon or Canon DSLRs (the Kenko ones are regarded as good enough for most uses, and certainly cheaper than Olympus ones) with suitable adapters. Image resolution through a microscope is usually lower than what the camera sensor can record, so I would not be too concerned about aberrations introduced by the teleconverter.
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Pau
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Joined: 20 Jan 2010
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PostPosted: Fri Feb 02, 2018 7:43 am    Post subject: Reply with quote

The 4/3 sensor has 21.6 mm diagonal. This is close enough to the field number of most objectives and eyepieces to do not produce vignette, so maybe the trinocular photoport or adapter could be limiting the field. Also you may be aware that many microscope objectives do need eyepiece complementary correction of objective aberrations "compensating eyepieces", if it's the case direct projection is not a good idea
In general 1.2 - 1.3X secondary magnification is to be recommended for 4/3 sensors with non wide field microscopes.

What microscope, objectives and adapter do you use?. Pictures would help to understand the issue.
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kit1980



Joined: 18 Aug 2016
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Location: Bellevue, WA, USA

PostPosted: Wed Mar 07, 2018 8:13 pm    Post subject: Reply with quote

To circle back, I've bought the teleconverter and it seems to work quite well for my purposes. Thanks everyone for your comments!
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Omax microscope with Nikon CF objectives
Olympus OM-D E-M10 Mark II camera
http://sdymphoto.com/
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rjlittlefield
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Joined: 01 Aug 2006
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PostPosted: Wed Mar 07, 2018 10:17 pm    Post subject: Reply with quote

Thanks for the follow-up.

Exactly which teleconverter did you buy?

--Rik
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kit1980



Joined: 18 Aug 2016
Posts: 123
Location: Bellevue, WA, USA

PostPosted: Wed Mar 07, 2018 10:24 pm    Post subject: Reply with quote

rjlittlefield wrote:
Exactly which teleconverter did you buy?

I've bought the only official teleconverter for micro four thirds cameras, Olympus M.Zuiko Digital MC-14 1.4x (rather expensive for a teleconverter at $300, but I hope to also use it with a compatible telephoto lens one day).
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http://sdymphoto.com/
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bralex



Joined: 22 Jan 2018
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Location: Colorado, USA

PostPosted: Sat Mar 10, 2018 9:27 am    Post subject: Reply with quote

I recently bought the teleconverter and the olympus pro 40-150 lens. I love the combination; the only fault I find is that the actual infinity focus is slightly "inside" the mark - I spent about an hour figuring that out! Smile
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enricosavazzi



Joined: 21 Nov 2009
Posts: 1046
Location: Stockholm, Sweden

PostPosted: Sat Mar 10, 2018 12:41 pm    Post subject: Reply with quote

bralex wrote:
I recently bought the teleconverter and the olympus pro 40-150 lens. I love the combination; the only fault I find is that the actual infinity focus is slightly "inside" the mark - I spent about an hour figuring that out! Smile

This is common in modern lenses, which are meant to be used mainly with autofocus. The "extra", or slightly "beyond infinity", focus capability is built into the system so that focusing at infinity remains possible even if the ambient temperature changes the actual focal length of the lens (and therefore its infinity focus) or, in the case of zooms, the lens does not focus parfocally at infinity at exactly the same extension at all focal lengths. The same applies to teleconverters (better allow for a little focusing beyond infinity, than come up short of it).

The only time this may become a problem in stills shooting is when the photographer manually sets the focus ring at infinity without checking the focus accuracy in the viewfinder/live view. This style of shooting was used in the past, especially before AF became available. Shooting movies still requires a zoom to be parfocal (or the use of precise manual focus pulling), because a hunting or abruptly readjusting AF would be annoying to viewers.
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Ichthyophthirius



Joined: 07 Mar 2013
Posts: 801

PostPosted: Sat Mar 10, 2018 2:18 pm    Post subject: Reply with quote

kit1980 wrote:
To circle back, I've bought the teleconverter and it seems to work quite well for my purposes.


Could you post an image of the setup (microscope, trinocular and teleconverter)? That would be nice for reference.

Regards, Ichty
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